Though discussions remain in early stages, sources confirmed to CNBC that Walmart is interested in strengthening its existing relationship with Humana HUM amid a rush of deal speculation in the industry.

People familiar with the matter cautioned that details of the deal remained vague and that it's possible one may never materialize.

"Under its current alliance with Walmart (which began in 2005), Humana stations representatives in Wal-Mart stores, Sam's Club locations and Neighborhood Markets across the country who seek to enroll Medicare-eligible individuals," said Credit Suisse analyst A.J. Rice. "By way of background, Humana operates its own pharmacy benefit manager that services its own health plan offerings. The PBM also has a state of the art mail order facility that has a strong specialty capability."

Still, any such move by Walmart WMT heightens attention on the remaining health insurance companies as potential partners for large retailers or other big companies in their efforts to expand into other sectors.

Online retail behemoth Amazon, J.P. Morgan Chase and Berkshire Hathaway also have teamed up to tackle rising employee health-care costs. CNBC also has reported that Amazon has participated in exploratory talks with generic drugmakers.